Hi, thanks.
Yes, it is a UK PSC.
As it is only myself in the Company, I don't have a contract of employment. I work in financial services as a contractor, so I do have contracts with the firms I contract to, though that would I imagine be difficult to explain in a visa app.
I was thinking of sending a letter as director as you describe it, but it would by me writing it about myself as I don't have a manager. I was also thinking of sending a copy of my Certificate of Incorporation, and maybe even latest accounts.
Thanks.